In France, the number plates on vehicles detail the part of the country the car and its occupants are from. But a new money-saving measure is about to change this system and, according to John Laurenson, the French may miss it once it has gone.

You have to change your number plates if you move to a new region

In England, children on long car journeys are encouraged to play "I spy with my little eye, something beginning with... R". "Road." "Your turn."

It is boring, but too much excitement is not good for kids.

The French have their very own tedious car game; spot the "département".

Because in France, your number plate ends with the two digits of the administrative district, or département, where you live.

One look at a French car and if you are good citizen of the Republic and have memorised all 100 départements, you can say where that car, and the people in it, are from.

If the number ends with 75, easy-peasy, that is Paris - the city that is a département in its own right. But the rest are more difficult and intentionally so.

National pride

The revolutionaries who created modern France in 1789 wanted to break down regional loyalties in order to build national consciousness, so they divided up 1,000-year-old provinces like Normandy and Brittany and their names disappeared from the map.

The countries Napoleon annexed went the same way.

Belgium, Holland, Germany and Italy were all turned into départements. So, more recently, was Algeria.

The new administrative divisions were mostly named after geographical features: rivers or mountain ranges usually, or more precisely stretches of river or subdivisions of mountain range.

Toulouse, for example, is in département number 31, the Haute-Garonne or upper reaches of the Garonne River. It is infernally complicated.

But dividing a national territory into 100 little bits, arranging them in alphabetical order and giving each one a number is precisely the sort of thing the French mean by the word they invented - "rationnel" (rational).

The fact that you have got your département's number on your plate means that if you go and live down the road in another département, you have got to go to the prefecture - because each département is policed by a representative of the state called a prefect - and get your car papers changed.

Then you have to go to the garage to get your number plates changed.

It is a senseless waste of time and money, serving only to reinforce a pathological obsession with order that belongs to another era.

And yet, apart from anything else, French people need them in order to retain even a feeble grasp of the administrative system they have been saddled with.

Administrative DNA

The time is long gone when rows of clean-cut children joyfully rote-learnt the départements in school.

Nowadays, you learn them sitting in traffic.

Go to Chartres, for example, and you will find yourself surrounded by cars with plates that end in 28 (Eure-et-Loir).

And do not say: "Who cares?"

Without that 28 you cannot get telephone information about local weather or trains.

You cannot use the directory enquiries on the internet; you will not even receive a letter if there is no 28 on the envelope because it is the start of the postcode.

Your two digits are even embedded in your social security number, the French citizen's administrative DNA.

And people grow quite attached to their numbers.

Once I was playing bingo in a village hall in the mountains above Carcassonne.

Every time the two digits of the local département came up a boy shouted: "Le beau pays!" (the beautiful land).

People laughed but nobody seriously doubted that God's own country is the 34.

Intruders beware

The main advantage of the current registration plates, though, is that they enable you to identify intruders who have dared motor into your home département.

Especially Parisians who have ventured out of the gates of the capital into the wilderness they call "Province" and where they are universally known by the derogatory term "Parigots".

When you see that 75 ahead of you, and they are dithering at a turning, a bit lost because they are a long way from home, the etiquette is to blast on the klaxon and shout: "Rentre chez toi, Parigot!" - Parisian, go home.

And your number plate does not only tell the rest of France where you are from, but in a rough, ready and probably quite unfair way, who you are.

According to those last two digits you will be considered a snob, a peasant or a rioter/drug dealer until you have proven otherwise.

People think twice about insulting drivers with plates that end 2A or 2B, the numbers of Corsica, in case they find their family locked in a blood feud that could last several generations.

If you hire a car in France, be aware that everybody else can see that fact and assume you are a hopeless foreigner because your licence number ends with 60.

For tax reasons, the big hire companies register their cars in the département where it is cheapest to do so - the Oise - le 60.

Dubious pleasures, those, of what will soon be France's old number plates.

A symbol in a small way of an archaic, inefficient fashion of doing things.

But one which many Frenchmen and women may miss when it is gone.

From Our Own Correspondent is broadcast on Thursday, 22 December, 2005 at 1100 GMT on BBC Radio 4. Please check the programme schedules for World Service transmission times.